Special Conditions: Airbus Model A321neo XLR Airplane; Electronic Flight-Control System: Lateral-Directional and Longitudinal Stability, and Low-Energy Awareness, 23507-23510 [2024-07139]
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Federal Register / Vol. 89, No. 66 / Thursday, April 4, 2024 / Rules and Regulations
a. The Nij (calculated in accordance
with 49 CFR 571.208) must be below
1.0, where Nij = Fz/Fzc + My/Myc, and
Nij critical values are:
i. Fzc = 1530 lbs. for tension
ii. Fzc = 1385 lbs. for compression
iii. Myc = 229 lb-ft in flexion
iv. Myc = 100 lb-ft in extension
b. In addition, peak Fz must be below
937 lbs. in tension and 899 lbs. in
compression.
c. Rotation of the head about its
vertical axis relative to the torso is
limited to 105 degrees in either
direction from forward facing.
d. The neck must not impact any
surface that would produce
concentrated loading on the neck.
4. Spine and Torso Injury Criteria
a. The lumbar spine tension (Fz)
cannot exceed 1200 lbs.
b. Significant concentrated loading on
the occupant’s spine, in the area
between the pelvis and shoulders
during impact, including rebound, is
not acceptable. During this type of
contact, the interval for any rearward (X
direction) acceleration exceeding 20g
must be less than 3 milliseconds as
measured by the thoracic
instrumentation specified in 49 CFR
part 572, subpart E filtered in
accordance with SAE International
(SAE) recommended practice J211/1,
‘‘Instrumentation for Impact Test—Part
1—Electronic Instrumentation.’’
c. The occupant must not interact
with the armrest or other seat
components in any manner significantly
different than would be expected for a
forward-facing seat installation.
5. Pelvis Criteria
Any part of the load-bearing portion
of the bottom of the ATD pelvis must
not translate beyond the edges of the
seat bottom seat-cushion supporting
structure.
6. Femur Criteria
Axial rotation of the upper leg (about
the z-axis of the femur per SAE
Recommended Practice J211/1) must be
limited to 35 degrees from the nominal
seated position. Evaluation during
rebound does not need to be considered.
ddrumheller on DSK120RN23PROD with RULES1
7. ATD and Test Conditions
Longitudinal tests conducted to
measure the injury criteria above must
be performed with the FAA Hybrid III
ATD, as described in SAE 1999–01–
1609, ‘‘A Lumbar Spine Modification to
the Hybrid III ATD for Aircraft Seat
Tests.’’ The tests must be conducted
with an undeformed floor, at the mostcritical yaw cases for injury, and with
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all lateral structural supports (e.g.,
armrests or walls) installed.
Note: Jet Aviation AG must demonstrate
that the installation of seats via plinths or
pallets meets all applicable requirements.
Compliance with the guidance contained in
Policy Memorandum PS–ANM–100–2000–
00123, ‘‘Guidance for Demonstrating
Compliance with Seat Dynamic Testing for
Plinths and Pallets,’’ dated February 2, 2000,
is acceptable to the FAA.
8. Inflatable Airbag Restraint Systems
Special Conditions
If inflatable airbag restraint systems
are installed, the airbag systems must
meet the requirements in Special
Conditions 25–386–SC, or other airbag
system special conditions which are
applicable to the Boeing Model 737
series airplanes.
Issued in Kansas City, Missouri, on March
22, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and
Standards Division, Aircraft Certification
Service.
[FR Doc. 2024–06894 Filed 4–3–24; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA–2021–1034; Special
Conditions No. 25–857–SC]
Special Conditions: Airbus Model
A321neo XLR Airplane; Electronic
Flight-Control System: LateralDirectional and Longitudinal Stability,
and Low-Energy Awareness
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions.
AGENCY:
These special conditions are
issued for the Airbus Model A321neo
XLR airplane. This airplane will have a
novel or unusual design feature when
compared to the state of technology
envisioned in the applicable
airworthiness standards. This design
feature is an electronic flight-control
system (EFCS) associated with lateraldirectional and longitudinal stability,
and low-energy awareness. The
applicable airworthiness regulations do
not contain adequate or appropriate
safety standards for this design feature.
These special conditions contain the
additional safety standards that the
Administrator considers necessary to
establish a level of safety equivalent to
that established by the existing
airworthiness standards.
SUMMARY:
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DATES:
23507
Effective April 4, 2024.
Troy
Brown, Performance and Environment
Unit, AIR–621A, Technical Policy
Branch, Policy and Standards Division,
Aircraft Certification Service, Federal
Aviation Administration, 1801 S Airport
Rd., Wichita, KS 67209–2190; telephone
and fax 405–666–1050; email
troy.a.brown@faa.gov.
FOR FURTHER INFORMATION CONTACT:
SUPPLEMENTARY INFORMATION:
Background
On September 16, 2019, Airbus
applied for an amendment to Type
Certificate No. A28NM to include the
new Model A321neo XLR airplane. This
airplane is a twin-engine, transportcategory airplane, with seating for 244
passengers, and a maximum takeoff
weight of 222,000 pounds.
Type Certification Basis
Under the provisions of 14 CFR
21.101, Airbus must show that the
Model A321neo XLR airplane meets the
applicable provisions of the regulations
listed in Type Certificate No. A28NM, or
the applicable regulations in effect on
the date of application for the change,
except for earlier amendments as agreed
upon by the FAA.
If the Administrator finds that the
applicable airworthiness regulations
(e.g., 14 CFR part 25) do not contain
adequate or appropriate safety standards
for the Airbus Model A321neo XLR
airplane because of a novel or unusual
design feature, special conditions are
prescribed under the provisions of
§ 21.16.
Special conditions are initially
applicable to the model for which they
are issued. Should the type certificate
for that model be amended later to
include any other model that
incorporates the same novel or unusual
design feature, or should any other
model already included on the same
type certificate be modified to
incorporate the same novel or unusual
design feature, these special conditions
would also apply to the other model
under § 21.101.
In addition to the applicable
airworthiness regulations and special
conditions, the Airbus Model A321neo
XLR airplane must comply with the
fuel-vent and exhaust-emission
requirements of 14 CFR part 34, and the
noise-certification requirements of 14
CFR part 36.
The FAA issues special conditions, as
defined in § 11.19, in accordance with
§ 11.38, and they become part of the
type certification basis under § 21.101.
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Federal Register / Vol. 89, No. 66 / Thursday, April 4, 2024 / Rules and Regulations
Novel or Unusual Design Feature
The Airbus Model A321neo XLR
airplane will incorporate the following
novel or unusual design feature:
An EFCS associated with lateraldirectional and longitudinal stability,
and low-energy awareness.
ddrumheller on DSK120RN23PROD with RULES1
Proposed Special Conditions
The FAA issued Notice of Proposed
Special Conditions No. FAA–2021–
1034, which was published in the
Federal Register on November 3, 2023
(88 FR 75517).
In that document, the FAA explained
that the Airbus’ proposed A321neo XLR
includes an EFCS, and that the control
laws of that system can result in neutral
static lateral-directional stability and
neutral static longitudinal stability,
insufficient feedback to the flightcrew
from the pitching moment, and
insufficient awareness that the airplane
is in a low-energy state. The FAA
therefore proposed that the applicable
airworthiness regulations are inadequate
or inappropriate to address these issues
and proposed special conditions to
address them.
The FAA proposed that in the absence
of positive lateral stability, the curve of
lateral control-surface deflections
against sideslip angle should be, in a
conventional sense and reasonably in
harmony with, rudder deflection during
steady-heading sideslip maneuvers.
The FAA further proposed that
because conventional relationships
between stick forces and control-surface
displacements do not apply to the
‘‘load-factor command’’ flight-control
system on the Airbus Model A321neo
XLR airplane, longitudinal stability
characteristics should be evaluated by
assessing the airplane’s handling
qualities during simulator and flight-test
maneuvers appropriate to operation of
the airplane. Additionally, under icing
and non-icing conditions there may be
a difference in full pedal deflection.
This difference may result in changes to
testing before reaching full pedal
deflection, and these special conditions
account for these differences.
The airplane must provide adequate
awareness cues to the pilot of a lowenergy (low-speed/low-thrust/lowheight) state to ensure that the airplane
retains sufficient energy to recover
when flight-control laws provide neutral
longitudinal stability significantly
below the normal operating speeds.
‘‘Adequate awareness’’ means that
information must be provided to alert
the crew of unsafe operating conditions
and to enable them to take appropriate
corrective action. Testing of these
awareness cues should occur by
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simulator and flight test in the
operational flight envelope for which
certification is requested. Testing
should include a sufficient number of
tests to allow the level of energy
awareness, and the effects of energymanagement errors, to be assessed.
Discussion of Comments and Final
Special Conditions
Airbus Commercial Aircraft (Airbus)
and The Boeing Company (Boeing)
submitted comments on the same
provision of the proposed special
conditions.
The Static Lateral-Directional
Stability section of the proposed special
conditions required the applicant to
conduct, in icing conditions, steady
heading sideslip maneuvers in several
configurations. The proposed conditions
would have required these sideslip
maneuvers to be conducted ‘‘over the
range of sideslip angles appropriate to
the operation of the airplane, but not
less than those obtained with one half
of available rudder control input.’’
Airbus and Boeing each
recommended that these maneuvers be
conducted with full pedal deflection but
recommended different approaches to
implement that change.
Airbus requested that the FAA add a
note stating that these maneuvers will
be continued beyond the sideslip angles
appropriate for normal operation of the
airplane and demonstrate that full pedal
travel can be safely applied. Airbus
stated that deflecting the pedals as
much as practicable in icing conditions
would provide a better coverage of the
intent of § 25.21(g) regarding § 25.177.
Further, Airbus stated that the addition
of this note would align FAA and EASA
standards.
Boeing recommended that the FAA
revise the special conditions to require
Airbus to conduct these sideslips ‘‘up to
the angle at which full rudder control is
used or a rudder control force of 180
pounds is obtained.’’ Boeing said this
change would be consistent with the
language of paragraph 4.15.2.3 of AC
25–25A, Performance and Handling
Characteristics in Icing Conditions.
AC 25–25A provides an acceptable
means of showing compliance with
certain requirements of part 25 of 14
CFR related to airplane performance and
handling characteristics in icing
conditions. To address static lateral
directional stability, the AC provides, as
examples of an acceptable test program,
that the applicant may conduct steady
heading sideslips, in certain
configurations, including ‘‘to full rudder
authority, 180 pounds of rudder pedal
force, or full lateral control authority.’’
Paragraph 4.15.2.3.
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The FAA agrees with the commenters
that full-pedal deflection meets the
intent of § 25.21(g) and aligns with
guidance in the referenced AC. The
FAA also agrees that this approach is
harmonized with EASA’s certification
approach 2 to this issue. The FAA finds
that it is unnecessary to revise the
condition as suggested by Boeing, and
that the language provided by Airbus,
with minor revision by the FAA,3 is
sufficient to address this issue.
These final special conditions correct
minor discrepancies in the numbering
of the proposed special conditions.
Also, the proposed special conditions
related to low energy awareness
contained three instances of ‘‘should.’’
The FAA has revised these to ‘‘must’’ in
these final special conditions, for
enforceability and for consistency with
the expectations of the FAA and the
applicant.
Other than these foregoing changes,
these special conditions are adopted as
proposed. The special conditions
contain the additional safety standards
that the Administrator considers
necessary to establish a level of safety
equivalent to that established by the
existing airworthiness standards.
Applicability
As discussed above, these special
conditions are applicable to the Airbus
Model A321neo XLR airplane. Should
Airbus apply at a later date for a change
to the type certificate to include another
model incorporating the same novel or
unusual design feature, these special
conditions would apply to that model as
well.
Under standard practice, the effective
date of final special conditions would
be 30 days after the date of publication
in the Federal Register. However, as the
certification date for the Airbus Model
A321neo XLR is imminent, the FAA
finds that good cause exists to make
these special conditions effective upon
publication.
Conclusion
This action affects only certain novel
or unusual design features on one model
series of airplane. It is not a rule of
general applicability.
2 EASA Certification Review Item (CRI) B–06,
‘‘Flight in Icing Conditions’’, issue 2, April 11,
2013.
3 Under the U.S. regulatory system, notes are
explanatory rather than mandatory. See, e.g.,
section 7.5 of the Document Drafting Handbook
(Aug. 2018 Edition, Rev. 2.1, dated Oct. 2023).
Therefore, in the final special conditions, the
recommended language is no longer a ‘‘note,’’ and
the commenter’s ‘‘will’’ is a ‘‘must.’’
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Federal Register / Vol. 89, No. 66 / Thursday, April 4, 2024 / Rules and Regulations
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements.
Authority Citation
The authority citation for these
special conditions is as follows:
Authority: 49 U.S.C. 106(f), 106(g), 40113,
44701, 44702, 44704.
The Special Conditions
■ Accordingly, pursuant to the
authority delegated to me by the
Administrator, the following special
conditions are issued as part of the type
certification basis for the Airbus Model
A321neo XLR airplane.
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Static Lateral-Directional Stability
(a) In lieu of compliance with
§ 25.171, the airplane must have lateral
and directional stability characteristics
in accordance with § 25.177. In
addition, both suitable stability and
suitable control feel are required in any
condition normally encountered in
service.
(b) In lieu of compliance with
§ 25.177(c), the following requirement
must be met for the configurations and
speed specified in § 25.177(a):
(1) In straight, steady sideslips over
the range of sideslip angles appropriate
to the operation of the airplane, the
directional control movements and
forces must be substantially
proportional to the angle of sideslip in
a stable sense. The factor of
proportionality must lie between limits
found necessary for safe operation.
During these straight, steady sideslips,
necessary lateral control movements
and forces must not be in the unstable
sense with the exception of speeds
above Vmo/Mmo per § 25.177(b)(2). The
range of sideslip angles evaluated must
include those sideslip angles resulting
from the lesser of:
(i) One-half of the available
directional (pedal) control input; and
(ii) A directional (pedal) control force
of 180 pounds.
(c) In lieu of compliance with
§ 25.177(d), the following requirements
must be met:
(1) In non-icing conditions, for
sideslip angles greater than those
prescribed by § 25.177(a), up to the
angle at which full rudder control is
used or a rudder control force of 180
pounds is obtained, the rudder control
forces may not reverse, and increased
rudder deflection must be needed for
increased angles of sideslip. Compliance
with this requirement must be shown
using straight, steady sideslips, unless
full lateral control input is achieved
before reaching either full rudder
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control input or a rudder control force
of 180 pounds; a straight, steady
sideslip need not be maintained after
achieving full lateral control input. This
requirement must be met at all approved
landing gear and flap positions for the
range of operating speeds and power
conditions appropriate to each landing
gear and flap position with all engines
operating.
(2) In icing conditions, in the
configurations listed below, trim the
airplane at the specified speed and
conduct steady heading sideslips over
the range of sideslip angles appropriate
to the operation of the airplane but not
less than those obtained with one-half of
available rudder control input.
(i) High lift devices retracted
configuration: trim at best rate of climb
speed but not less than minimum all
engines operating climb speed defined
for icing conditions.
(ii) Lowest lift take-off configuration:
trim at the all-engines operating initial
climb speed defined for icing
conditions.
(iii) Landing configurations: trim at
minimum landing speed defined for
icing conditions.
The steady heading sideslip maneuver
must be continued beyond sideslip
angles appropriate for normal operation
of the airplane to demonstrate full pedal
can be safely applied unless justification
for smaller input is provided (e.g., heavy
buffet that would deter the pilot from
further deflecting the pedals and would
make investigations to full pedal a
potential flight test safety concern, or
pedal input required for normal
operations significantly smaller than
full pedal).
Longitudinal Stability
In lieu of compliance with the
requirements of §§ 25.171, 25.173, and
25.175, the airplane must be shown to
have longitudinal stability
characteristics in accordance with the
following conditions. In addition, both
suitable stability and suitable control
feel are required in any condition
normally encountered in service,
including the effects of atmospheric
disturbance.
(a) Strong positive static longitudinal
stability (1 pound per 6 knots applied
through the sidestick) must be present
which provides adequate awareness
cues to the crew that the speed is above
Vmo/Mmo or below the minimum speed
for hands-free stabilized flight. Static
longitudinal characteristics must be
shown to be suitable based on the
airplane handling qualities, including
an evaluation of pilot workload and
pilot compensation, for specific test
procedures during the flight-test
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23509
evaluations. These characteristics must
be shown for appropriate combinations
of airplane configuration (i.e., flaps
extended or retracted, gear deployed or
stowed) and thrust for climb, cruise,
approach, landing, and go-around.
(1) Release of the controller at speeds
above Vmo/Mmo, or below the minimum
speed for hands-free stabilized flight,
must produce a prompt recovery
towards normal operating speeds
without resulting in a hazardous
condition.
(2) The design must not allow a pilot
to re-trim the controller forces resulting
from this stability.
Low Energy Awareness
The airplane must provide adequate
awareness cues to the pilot of a lowenergy (low-speed/low-thrust/lowheight) state to ensure that the airplane
retains sufficient energy to recover
when flight-control laws provide neutral
longitudinal stability significantly
below the normal operating speeds. This
must be accomplished as follows:
(a) Adequate low speed/low thrust
cues at low altitude should be provided
by a strong positive static stability force
gradient (1 pound per 6 knots applied
through the sidestick), or
(b) The low energy awareness must be
provided by an appropriate warning
with the following characteristics. The
low-energy awareness must:
(1) Be unique, unambiguous, and
unmistakable.
(2) Be active at appropriate altitudes
and in appropriate configurations (i.e.,
at low altitude, in the approach and
landing configurations).
(3) Be sufficiently timely to allow
recovery to a stabilized flight condition
inside the normal flight envelope while
maintaining the desired flight path and
without entering the flight controls
angle-of-attack protection mode.
(4) Not be triggered during normal
operation, including operation in
moderate turbulence for recommended
maneuvers at recommended speeds.
(5) Not be cancelable by the pilot
other than by achieving a higher energy
state.
(6) Have an adequate hierarchy among
the various warnings so that the pilot is
not confused and led to take
inappropriate recovery action if
multiple warnings occur.
Global energy awareness and nonnuisance on low-energy cues must be
evaluated by simulator and flight tests
in the whole take-off and landing
altitude range for which certification is
requested. This includes all relevant
combinations of weight, center-ofgravity position, configuration, airbrakes
position, and available thrust, including
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Federal Register / Vol. 89, No. 66 / Thursday, April 4, 2024 / Rules and Regulations
reduced and derated take-off thrust
operations and engine-failure cases. The
tests must assess the level of energy
awareness, and the effects of energymanagement errors.
Issued in Kansas City, Missouri, on March
28, 2024.
Patrick R. Mullen,
Manager, Technical Innovation Policy
Branch, Policy and Innovation Division,
Aircraft Certification Service.
[FR Doc. 2024–07139 Filed 4–3–24; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 71
[Docket No. FAA–2023–1906; Airspace
Docket No. 22–AWA–3]
RIN 2120–AA66
Amendment of Class C Airspace; San
Juan Luis Munoz Marin International
Airport, PR
Federal Aviation
Administration (FAA), DOT.
ACTION: Final rule.
AGENCY:
This action modifies the San
Juan Luis Munoz Marin International
Airport, PR (SJU), Class C airspace by
adding a cutout to the surface area near
the Fernando Luis Ribas Dominicci
Airport, PR (SIG). The FAA is taking
this action to enhance safety and enable
more efficient operations at SJU and
SIG.
SUMMARY:
Effective date 0901 UTC, July 11,
2024. The Director of the Federal
Register approves this incorporation by
reference action under 1 CFR part 51,
subject to the annual revision of FAA
Order 7400.11 and publication of
conforming amendments.
ADDRESSES: A copy of the Notice of
Proposed Rulemaking (NPRM), all
comments received, this final rule, and
all background material may be viewed
online at www.regulations.gov using the
FAA Docket number. Electronic
retrieval help and guidelines are
available on the website. It is available
24 hours each day, 365 days each year.
FAA Order JO 7400.11H, Airspace
Designations and Reporting Points, and
subsequent amendments can be viewed
online at www.faa.gov/air_traffic/
publications/. You may also contact the
Rules and Regulations Group, Office of
Policy, Federal Aviation
Administration, 800 Independence
Avenue SW, Washington, DC 20591;
telephone: (202) 267–8783.
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DATES:
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FOR FURTHER INFORMATION CONTACT:
Brian Vidis, Rules and Regulations
Group, Office of Policy, Federal
Aviation Administration, 800
Independence Avenue SW, Washington
DC 20591; telephone: (202) 267–8783.
SUPPLEMENTARY INFORMATION:
Authority for This Rulemaking
The FAA’s authority to issue rules
regarding aviation safety is found in
Title 49 of the United States Code.
Subtitle I, Section 106 describes the
authority of the FAA Administrator.
Subtitle VII, Aviation Programs,
describes in more detail the scope of the
agency’s authority. This rulemaking is
promulgated under the authority
described in Subtitle VII, Part A,
Subpart I, Section 40103. Under that
section, the FAA is charged with
prescribing regulations to assign the use
of the airspace necessary to ensure the
safety of aircraft and the efficient use of
airspace. This regulation is within the
scope of that authority as it modifies
terminal airspace as required to preserve
the safe and efficient flow of air traffic
in the San Juan, PR, area.
History
The FAA published a NPRM for
Docket No. FAA–2023–1906 in the
Federal Register (88 FR 68509; October
4, 2023) proposing to modify the Class
C airspace area surrounding SJU.
Interested parties were invited to
participate in this rulemaking effort by
submitting written comments on the
proposal. One comment was received
from the Air Line Pilots Association
International in support of the new SJU
Class C airspace design.
Differences From the NPRM
Subsequent to publication of the
NPRM, the FAA identified that the SJU
Airport Reference Point (ARP)
geographic coordinates listed in the
Class C airspace description had been
rounded in error and published as ‘‘lat.
18°26′22″ N, long. 66°00′07″ W’’. The
correct ARP for SJU is ‘‘lat. 18°26′22″ N,
long. 066°00′08″ W’’. The ARP for SJU
is changed from ‘‘lat. 18°26′22″ N, long.
66°00′07″ W’’ to ‘‘lat. 18°26′22″ N, long.
066°00′08″W’’. This final rule corrects
the error.
Incorporation by Reference
Class C airspace designations are
published in paragraph 4000 of FAA
Order JO 7400.11, Airspace
Designations and Reporting Points,
which is incorporated by reference in 14
CFR 71.1 on an annual basis. This
document amends the current version of
that order, FAA Order JO 7400.11H,
dated August 11, 2023, and effective
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September 15, 2023. FAA Order JO
7400.11H is publicly available as listed
in the ADDRESSES section of this
document. This amendment will be
published in the next update to FAA
Order JO 7400.11.
FAA Order JO 7400.11H lists Class A,
B, C, D, and E airspace areas, air traffic
service routes, and reporting points.
The Rule
This action amends 14 CFR part 71 by
modifying the San Juan Luis Munoz
Marin International Airport (SJU), PR,
Class C airspace description by adding
a cutout to the Class C surface area
northwest of SJU from the surface to but
not including 1,200 feet above mean sea
level (MSL). This amendment enhances
flight safety by allowing aircraft
departing runway 9 at Fernando Luis
Ribas Dominicci Airport, PR (SIG),
when the SIG air traffic control tower is
closed, the ability to either remain
outside of the San Juan, PR, Class C
airspace by turning to the north and
west or to have additional time to
establish two-way radio communication
with the San Juan air traffic control
tower prior to entering the San Juan, PR,
(SJU) Class C airspace.
Additionally, the FAA corrects the
first line of the Class C airspace
description header information by only
listing the city and territory location of
the airport. This change follows the
FAA’s current airspace description
format guidance.
Regulatory Notices and Analyses
The FAA considers the impacts of
regulatory actions under a variety of
executive orders and other
requirements. First, Executive Order
12866 and Executive Order 13563 direct
that each Federal agency shall propose
or adopt a regulation only upon a
reasoned determination that the benefits
of the intended regulation justify the
costs. Second, the Regulatory Flexibility
Act of 1980 (Pub. L. 96–354) requires
agencies to analyze the economic
impact of regulatory changes on small
entities. Third, the Trade Agreements
Act (Pub. L. 96–39) prohibits agencies
from setting standards that create
unnecessary obstacles to the foreign
commerce of the United States. Fourth,
the Unfunded Mandates Reform Act of
1995 (Pub. L. 104–4) requires agencies
to prepare a written assessment of the
costs, benefits, and other effects of
proposed or final rules that include a
Federal mandate that may result in the
expenditure by State, local, and tribal
governments, in the aggregate, or by the
private sector, of $100,000,000 or more
(adjusted annually for inflation) in any
one year. The current threshold after
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]]>Agencies
[Federal Register Volume 89, Number 66 (Thursday, April 4, 2024)]
[Rules and Regulations]
[Pages 23507-23510]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-07139]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2021-1034; Special Conditions No. 25-857-SC]
Special Conditions: Airbus Model A321neo XLR Airplane; Electronic
Flight-Control System: Lateral-Directional and Longitudinal Stability,
and Low-Energy Awareness
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Airbus Model
A321neo XLR airplane. This airplane will have a novel or unusual design
feature when compared to the state of technology envisioned in the
applicable airworthiness standards. This design feature is an
electronic flight-control system (EFCS) associated with lateral-
directional and longitudinal stability, and low-energy awareness. The
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for this design feature. These special
conditions contain the additional safety standards that the
Administrator considers necessary to establish a level of safety
equivalent to that established by the existing airworthiness standards.
DATES: Effective April 4, 2024.
FOR FURTHER INFORMATION CONTACT: Troy Brown, Performance and
Environment Unit, AIR-621A, Technical Policy Branch, Policy and
Standards Division, Aircraft Certification Service, Federal Aviation
Administration, 1801 S Airport Rd., Wichita, KS 67209-2190; telephone
and fax 405-666-1050; email [email protected].
SUPPLEMENTARY INFORMATION:
Background
On September 16, 2019, Airbus applied for an amendment to Type
Certificate No. A28NM to include the new Model A321neo XLR airplane.
This airplane is a twin-engine, transport-category airplane, with
seating for 244 passengers, and a maximum takeoff weight of 222,000
pounds.
Type Certification Basis
Under the provisions of 14 CFR 21.101, Airbus must show that the
Model A321neo XLR airplane meets the applicable provisions of the
regulations listed in Type Certificate No. A28NM, or the applicable
regulations in effect on the date of application for the change, except
for earlier amendments as agreed upon by the FAA.
If the Administrator finds that the applicable airworthiness
regulations (e.g., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the Airbus Model A321neo XLR airplane
because of a novel or unusual design feature, special conditions are
prescribed under the provisions of Sec. 21.16.
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same novel or
unusual design feature, or should any other model already included on
the same type certificate be modified to incorporate the same novel or
unusual design feature, these special conditions would also apply to
the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Airbus Model A321neo XLR airplane must comply with the
fuel-vent and exhaust-emission requirements of 14 CFR part 34, and the
noise-certification requirements of 14 CFR part 36.
The FAA issues special conditions, as defined in Sec. 11.19, in
accordance with Sec. 11.38, and they become part of the type
certification basis under Sec. 21.101.
[[Page 23508]]
Novel or Unusual Design Feature
The Airbus Model A321neo XLR airplane will incorporate the
following novel or unusual design feature:
An EFCS associated with lateral-directional and longitudinal
stability, and low-energy awareness.
Proposed Special Conditions
The FAA issued Notice of Proposed Special Conditions No. FAA-2021-
1034, which was published in the Federal Register on November 3, 2023
(88 FR 75517).
In that document, the FAA explained that the Airbus' proposed
A321neo XLR includes an EFCS, and that the control laws of that system
can result in neutral static lateral-directional stability and neutral
static longitudinal stability, insufficient feedback to the flightcrew
from the pitching moment, and insufficient awareness that the airplane
is in a low-energy state. The FAA therefore proposed that the
applicable airworthiness regulations are inadequate or inappropriate to
address these issues and proposed special conditions to address them.
The FAA proposed that in the absence of positive lateral stability,
the curve of lateral control-surface deflections against sideslip angle
should be, in a conventional sense and reasonably in harmony with,
rudder deflection during steady-heading sideslip maneuvers.
The FAA further proposed that because conventional relationships
between stick forces and control-surface displacements do not apply to
the ``load-factor command'' flight-control system on the Airbus Model
A321neo XLR airplane, longitudinal stability characteristics should be
evaluated by assessing the airplane's handling qualities during
simulator and flight-test maneuvers appropriate to operation of the
airplane. Additionally, under icing and non-icing conditions there may
be a difference in full pedal deflection. This difference may result in
changes to testing before reaching full pedal deflection, and these
special conditions account for these differences.
The airplane must provide adequate awareness cues to the pilot of a
low-energy (low-speed/low-thrust/low-height) state to ensure that the
airplane retains sufficient energy to recover when flight-control laws
provide neutral longitudinal stability significantly below the normal
operating speeds. ``Adequate awareness'' means that information must be
provided to alert the crew of unsafe operating conditions and to enable
them to take appropriate corrective action. Testing of these awareness
cues should occur by simulator and flight test in the operational
flight envelope for which certification is requested. Testing should
include a sufficient number of tests to allow the level of energy
awareness, and the effects of energy-management errors, to be assessed.
Discussion of Comments and Final Special Conditions
Airbus Commercial Aircraft (Airbus) and The Boeing Company (Boeing)
submitted comments on the same provision of the proposed special
conditions.
The Static Lateral-Directional Stability section of the proposed
special conditions required the applicant to conduct, in icing
conditions, steady heading sideslip maneuvers in several
configurations. The proposed conditions would have required these
sideslip maneuvers to be conducted ``over the range of sideslip angles
appropriate to the operation of the airplane, but not less than those
obtained with one half of available rudder control input.''
Airbus and Boeing each recommended that these maneuvers be
conducted with full pedal deflection but recommended different
approaches to implement that change.
Airbus requested that the FAA add a note stating that these
maneuvers will be continued beyond the sideslip angles appropriate for
normal operation of the airplane and demonstrate that full pedal travel
can be safely applied. Airbus stated that deflecting the pedals as much
as practicable in icing conditions would provide a better coverage of
the intent of Sec. 25.21(g) regarding Sec. 25.177. Further, Airbus
stated that the addition of this note would align FAA and EASA
standards.
Boeing recommended that the FAA revise the special conditions to
require Airbus to conduct these sideslips ``up to the angle at which
full rudder control is used or a rudder control force of 180 pounds is
obtained.'' Boeing said this change would be consistent with the
language of paragraph 4.15.2.3 of AC 25-25A, Performance and Handling
Characteristics in Icing Conditions.
AC 25-25A provides an acceptable means of showing compliance with
certain requirements of part 25 of 14 CFR related to airplane
performance and handling characteristics in icing conditions. To
address static lateral directional stability, the AC provides, as
examples of an acceptable test program, that the applicant may conduct
steady heading sideslips, in certain configurations, including ``to
full rudder authority, 180 pounds of rudder pedal force, or full
lateral control authority.'' Paragraph 4.15.2.3.
The FAA agrees with the commenters that full-pedal deflection meets
the intent of Sec. 25.21(g) and aligns with guidance in the referenced
AC. The FAA also agrees that this approach is harmonized with EASA's
certification approach \2\ to this issue. The FAA finds that it is
unnecessary to revise the condition as suggested by Boeing, and that
the language provided by Airbus, with minor revision by the FAA,\3\ is
sufficient to address this issue.
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\2\ EASA Certification Review Item (CRI) B-06, ``Flight in Icing
Conditions'', issue 2, April 11, 2013.
\3\ Under the U.S. regulatory system, notes are explanatory
rather than mandatory. See, e.g., section 7.5 of the Document
Drafting Handbook (Aug. 2018 Edition, Rev. 2.1, dated Oct. 2023).
Therefore, in the final special conditions, the recommended language
is no longer a ``note,'' and the commenter's ``will'' is a ``must.''
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These final special conditions correct minor discrepancies in the
numbering of the proposed special conditions. Also, the proposed
special conditions related to low energy awareness contained three
instances of ``should.'' The FAA has revised these to ``must'' in these
final special conditions, for enforceability and for consistency with
the expectations of the FAA and the applicant.
Other than these foregoing changes, these special conditions are
adopted as proposed. The special conditions contain the additional
safety standards that the Administrator considers necessary to
establish a level of safety equivalent to that established by the
existing airworthiness standards.
Applicability
As discussed above, these special conditions are applicable to the
Airbus Model A321neo XLR airplane. Should Airbus apply at a later date
for a change to the type certificate to include another model
incorporating the same novel or unusual design feature, these special
conditions would apply to that model as well.
Under standard practice, the effective date of final special
conditions would be 30 days after the date of publication in the
Federal Register. However, as the certification date for the Airbus
Model A321neo XLR is imminent, the FAA finds that good cause exists to
make these special conditions effective upon publication.
Conclusion
This action affects only certain novel or unusual design features
on one model series of airplane. It is not a rule of general
applicability.
[[Page 23509]]
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
Authority Citation
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702,
44704.
The Special Conditions
[squf] Accordingly, pursuant to the authority delegated to me by
the Administrator, the following special conditions are issued as part
of the type certification basis for the Airbus Model A321neo XLR
airplane.
Static Lateral-Directional Stability
(a) In lieu of compliance with Sec. 25.171, the airplane must have
lateral and directional stability characteristics in accordance with
Sec. 25.177. In addition, both suitable stability and suitable control
feel are required in any condition normally encountered in service.
(b) In lieu of compliance with Sec. 25.177(c), the following
requirement must be met for the configurations and speed specified in
Sec. 25.177(a):
(1) In straight, steady sideslips over the range of sideslip angles
appropriate to the operation of the airplane, the directional control
movements and forces must be substantially proportional to the angle of
sideslip in a stable sense. The factor of proportionality must lie
between limits found necessary for safe operation. During these
straight, steady sideslips, necessary lateral control movements and
forces must not be in the unstable sense with the exception of speeds
above Vmo/Mmo per Sec. 25.177(b)(2). The range
of sideslip angles evaluated must include those sideslip angles
resulting from the lesser of:
(i) One-half of the available directional (pedal) control input;
and
(ii) A directional (pedal) control force of 180 pounds.
(c) In lieu of compliance with Sec. 25.177(d), the following
requirements must be met:
(1) In non-icing conditions, for sideslip angles greater than those
prescribed by Sec. 25.177(a), up to the angle at which full rudder
control is used or a rudder control force of 180 pounds is obtained,
the rudder control forces may not reverse, and increased rudder
deflection must be needed for increased angles of sideslip. Compliance
with this requirement must be shown using straight, steady sideslips,
unless full lateral control input is achieved before reaching either
full rudder control input or a rudder control force of 180 pounds; a
straight, steady sideslip need not be maintained after achieving full
lateral control input. This requirement must be met at all approved
landing gear and flap positions for the range of operating speeds and
power conditions appropriate to each landing gear and flap position
with all engines operating.
(2) In icing conditions, in the configurations listed below, trim
the airplane at the specified speed and conduct steady heading
sideslips over the range of sideslip angles appropriate to the
operation of the airplane but not less than those obtained with one-
half of available rudder control input.
(i) High lift devices retracted configuration: trim at best rate of
climb speed but not less than minimum all engines operating climb speed
defined for icing conditions.
(ii) Lowest lift take-off configuration: trim at the all-engines
operating initial climb speed defined for icing conditions.
(iii) Landing configurations: trim at minimum landing speed defined
for icing conditions.
The steady heading sideslip maneuver must be continued beyond
sideslip angles appropriate for normal operation of the airplane to
demonstrate full pedal can be safely applied unless justification for
smaller input is provided (e.g., heavy buffet that would deter the
pilot from further deflecting the pedals and would make investigations
to full pedal a potential flight test safety concern, or pedal input
required for normal operations significantly smaller than full pedal).
Longitudinal Stability
In lieu of compliance with the requirements of Sec. Sec. 25.171,
25.173, and 25.175, the airplane must be shown to have longitudinal
stability characteristics in accordance with the following conditions.
In addition, both suitable stability and suitable control feel are
required in any condition normally encountered in service, including
the effects of atmospheric disturbance.
(a) Strong positive static longitudinal stability (1 pound per 6
knots applied through the sidestick) must be present which provides
adequate awareness cues to the crew that the speed is above
Vmo/Mmo or below the minimum speed for hands-free
stabilized flight. Static longitudinal characteristics must be shown to
be suitable based on the airplane handling qualities, including an
evaluation of pilot workload and pilot compensation, for specific test
procedures during the flight-test evaluations. These characteristics
must be shown for appropriate combinations of airplane configuration
(i.e., flaps extended or retracted, gear deployed or stowed) and thrust
for climb, cruise, approach, landing, and go-around.
(1) Release of the controller at speeds above Vmo/
Mmo, or below the minimum speed for hands-free stabilized
flight, must produce a prompt recovery towards normal operating speeds
without resulting in a hazardous condition.
(2) The design must not allow a pilot to re-trim the controller
forces resulting from this stability.
Low Energy Awareness
The airplane must provide adequate awareness cues to the pilot of a
low-energy (low-speed/low-thrust/low-height) state to ensure that the
airplane retains sufficient energy to recover when flight-control laws
provide neutral longitudinal stability significantly below the normal
operating speeds. This must be accomplished as follows:
(a) Adequate low speed/low thrust cues at low altitude should be
provided by a strong positive static stability force gradient (1 pound
per 6 knots applied through the sidestick), or
(b) The low energy awareness must be provided by an appropriate
warning with the following characteristics. The low-energy awareness
must:
(1) Be unique, unambiguous, and unmistakable.
(2) Be active at appropriate altitudes and in appropriate
configurations (i.e., at low altitude, in the approach and landing
configurations).
(3) Be sufficiently timely to allow recovery to a stabilized flight
condition inside the normal flight envelope while maintaining the
desired flight path and without entering the flight controls angle-of-
attack protection mode.
(4) Not be triggered during normal operation, including operation
in moderate turbulence for recommended maneuvers at recommended speeds.
(5) Not be cancelable by the pilot other than by achieving a higher
energy state.
(6) Have an adequate hierarchy among the various warnings so that
the pilot is not confused and led to take inappropriate recovery action
if multiple warnings occur.
Global energy awareness and non-nuisance on low-energy cues must be
evaluated by simulator and flight tests in the whole take-off and
landing altitude range for which certification is requested. This
includes all relevant combinations of weight, center-of-gravity
position, configuration, airbrakes position, and available thrust,
including
[[Page 23510]]
reduced and derated take-off thrust operations and engine-failure
cases. The tests must assess the level of energy awareness, and the
effects of energy-management errors.
Issued in Kansas City, Missouri, on March 28, 2024.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation
Division, Aircraft Certification Service.
[FR Doc. 2024-07139 Filed 4-3-24; 8:45 am]
BILLING CODE 4910-13-P
